DONETSK, Ukraine — Wearing a black shirt and white clerical collar, the pastor walked into the occupied government building that serves as rebel headquarters in this eastern Ukrainian city. Serhiy Kosyak had come to plead for leniency: Rebels threatened to kill anyone who visited the small prayer vigils he held for Ukrainian unity, the city’s last open resistance to the separatist republic rebels had declared. As he waited for an audience, he saw an old friend among the gunmen milling around. Kosyak asked how he was doing. The man’s eyes stared back at him with hate.

There’s a moment on the slide to civil war where friends and neighbors become hard to recognize. The man screamed that Kosyak was a traitor and spy, an outburst sure to doom him amid the fevered atmosphere in the building, where suspicions ran high. Kosyak, 38, had seen the same anger in the passersby who sometimes accosted his pro-Ukraine prayer tent. And he saw it now in the rebels who tied him to a chair in the building and beat him as he prayed. He thought there was evil in it — real evil, because he believed in such things. He thought Satan grabbed hold of people with the ideas pouring into Donetsk on the Russian airwaves: that Russian-speakers there were in danger and needed to rise against Ukraine’s government. When the beatings finally stopped, and he was cleared for release, he stayed in his chair for a minute to bless his assailants: God, enter their lives and open their eyes.

Kosyak was still bruised a deep purple under his dress shirt when he opened his sidewalk service more than a week later, on the last day of May. The interfaith vigils once drew hundreds, but attendance was fading as worried supporters fled. Thirty people stood at the edge of a busy bridge beneath an intermittent rain. The sermons were about Sodom: a biblical city so overrun with evil that God decided it couldn’t be saved. In Genesis 19, angels send away a man named Lot, Sodom’s last good soul. Then the Lord levels it from the skies. “God didn’t destroy Sodom until Lot left,” said a pastor named Pavel Zaystev, 46. “As long as we’re here, there’s still hope.”

But he worried privately that Donetsk was beyond redemption. “You don’t think even some miracle could change them,” he said of the rebels. “That’s why I think of Sodom: God destroyed them because he could not change them.”

Ukraine’s corrupt president, Viktor Yanukovych, a native of the Donetsk region and Russian ally, was ousted by a popular uprising in Kiev on Feb. 22. The conflict came to Russian-speaking Donetsk, where about half of the 1 million residents are ethnically Russian, soon afterward, initially with small demonstrations. Protesters worried that the new government would punish Russian-speakers — fears fueled by Kremlin propaganda. They believed that their language would be banned and that fascists from Kiev were coming to hurt them. At first, the so-called fascists they had in mind were members of the Right Sector, a fringe ultra-nationalist group that had played an outsized role on the front lines of the protests in Kiev, but soon the label included the new government and its supporters, who had largely ignored their concerns. Then the protesters were storming government buildings as Russia warned that it would intervene, if needed, to protect its “compatriots.” They called for a referendum on secession, like the one that saw Russia annex Crimea in March, and they took up arms. Polls showed that most Donetsk residents wanted to remain in Ukraine, but outspoken opponents of the separatists began fleeing the city amid abductions and death threats. Some who remained deleted their Facebook pages, wondering who among their friends might be tracking their loyalties. “Fear is like a virus,” one said.

But there was still hope for peace in Donetsk, the political nexus for eastern Ukraine’s separatists and an important economic hub, even as fighting flared elsewhere. Throughout the spring, some residents had looked ahead to two events that might swing things back toward normalcy: Ukraine holding fresh presidential elections and Russia recalling the troops massed along the border nearby. Both came to pass, but they did nothing to stop the conflict from surging ahead. Each side had already come to see the battle as one between irreconcilable ideas — with an enemy that had to be eradicated. The fabric that let two groups of people with their own histories coexist in post-Soviet Ukraine had been ripped away. “This city needs to be cleansed,” warned a Catholic priest at the unity vigil, and on another evening, inside an expanding, makeshift armory, a rebel in a flannel shirt said, “There is some dirt here now, and we have to clean it from our land.”

On the afternoon before the vigil, a rebel commander from Russia sat before a bottle of bourbon at a faded desk and outlined his mission, which he said served God.

He was in a bright office at the end of an unlit hall, inside a compound that used to house the Ukrainian security service. He had a welcoming smile and tattoos that ran down his arms and peeked out from his crew neck. He was a leader in a group called the Russian Orthodox Army, and he went by the nickname Veren, or “the faithful.”

“First of all it’s purification of the land — purification from fascists,” Veren said. He described an awakening of Russian identity centered on Donetsk, where it was under threat, and he seemed to be an incarnation of the ideology the pastor had seen on the Russian airwaves, personally spreading it by hand.

Just a few weeks earlier, he had been overseeing what seemed like a small outlaw empire from the fifth floor of the rebel headquarters, the former government building, where masked men roamed the halls and speakers blared Soviet anthems from behind sprawling barricades. As separatist politicians scurried about overhead one day, Veren said he concerned himself with “special operations” — kidnappings and interrogations. Armed men kept handing him keys to cars they’d taken from their enemies. He has since been expanding his power, trading his spot in the crowded building for the more exclusive digs of the security compound, where men with assault rifles blocked the approaches and access was controlled with an intensity that felt paranoid. The Russian Orthodox Army’s seal of a Christendom-evoking sword and shield was stenciled onto each concrete block of one outer wall. On the wall across the street, another set of rebels, the highly professional Vostok battalion, had done the same, marking turf of their own.

In the new office, a Russian flag with the army’s logo hung from a bookshelf, and portraits of a fierce-looking Jesus were taped to the walls. Stickers and insignia patches sat on the desk. The first edition of the army’s newsletter had just arrived, and beneath its banner were recruitment phone numbers. It also had a website. Veren saw untapped potential in the Donetsk region’s 5 million people — and maybe across the Russian-speaking world. “People support us, but they’re afraid to take the first step,” he said. “I’m interested in any kind of promotion that gets the flow of people going.”

They had even released a promotional rap video featuring gunmen packed into the same office. It got 200,000 YouTube views in less than a week. Veren bounced his head and lip-synched the lyrics as he twisted a computer monitor around:

Till last fighter, till the victorious, glorious end
On the battlefield. Russian Orthodox!
Who if not us? When if not now?
Mom, I’m sorry. Nobody but us.

Like many of the Russian nationals operating in Donetsk, Veren was something of an enigma: The dark tasks he said he employed didn’t match his amiable demeanor. He had no military experience, he said; he’d once owned a fast food chain, where he picked up his knack for marketing. He was a 34-year-old from Sochi, but his wife was from Donetsk. Rumors of covert Russian soldiers and spies — and financial and military aid — had swirled around the conflict, but Veren said he had no contact with the Russian government. He said he got his start in the separatist movement by attending the protests that erupted in March.

If he was a demon to the pastors at the prayer vigil, he was also a protector of local separatists, who believed they were largely on their own against the Ukrainian army and what they saw as its fascist allies. They worried that if enough civilians left the city, the government might bomb it.

A recruit walked into Veren’s office. Overweight and nervous-looking in a button-down shirt, the young professional, 28, wasn’t built for war. But he wanted to help — he and Veren discussed whether he might do some managerial work, maybe go on neighborhood patrols. “Because I’m a conscious person,” he said when asked why he wanted to join. “And when bad things come to your house, a conscious person can’t ignore them.”

With much of the whiskey, brought to the meeting as a gift, now gone, Veren described a more ambitious quality to the conflict at hand. “The Russian person should remain Russian in any nationality and any land,” he said. The rebels gathered with him in the room — some locals and others Russian — likewise spoke about their battle as if it were about more than Donetsk. One man called it a “historical conflict,” another “a conflict of mentalities.” A likeness of St. George the dragon-slayer graced the army’s flag because Russians throughout history had fought under his banner. Veren said he had started groups in nearby hotspots like Mariupol and Slavyansk — and also had his eye on Kiev, Serbia, Georgia.

But first he was building his franchise in Donetsk. Someone put the keys to an Audi on his desk. The car’s registration showed that it belonged to the company of Serhiy Taruta, the billionaire steel magnate and regional governor. Taruta had fled to Kiev recently because of death threats. Veren went down to the compound’s parking garage, empty except for a couple rows of commandeered vehicles, neatly parked. A man waiting there appeared to be working as valet.

Veren got into the Audi’s driver’s seat. “This is a good car. I’ll trade it for 20 AK-47s,” he said. It was just past sunset, and the compound was quiet as guards opened the gate so Veren could ease the car from the sealed-off rebel zone. Then he jammed the gas and sped through the city’s quiet streets.

Later, as Veren and his comrades settled into a long dinner in a way that felt suddenly normal for a Friday night — they were the big, boisterous group at the restaurant carrying on happily as fellow diners tried not to mind — Fyodor, the intense young Russian who had designed the Army’s flag, gave a lesson on history. Russians made their great advances, he said, in huge, sudden leaps. The pace seems slow; the momentum builds. Then comes the exhilarating wave. “We must only run,” Fyodor said, seeming not to care where this moment would take him. “The end — it is nothing. Run to progress. Run to more.”

With darkness falling on a recent Sunday, a rebel in his fifties named Oleg wheeled a compact sedan through the city, his big frame packed into the driver’s seat. A veteran of the feared Berkut riot police, he still carried a natural authority, with his shaved head and intense blue eyes. He was headed to the airport, where a battle on May 26 had shocked the city with its violence. A mechanic who lived nearby would later remember seeing dead civilians along the roadside as he sped home to get his dog; a soldier at the airport recalled getting orders to hold fire as rebels massed outside, then watching in awe when fighter jets arrived. The bloodshed, with at least 50 rebels killed, showed that war was closing on Donetsk, and some rebels embraced it. Others, like Oleg, seemed deeply shaken. Asked if he’d been at the airport that day, he paused, looked down, and said, “Yes.”

Donetsk — a relatively affluent city with riverside parks and a sparkling soccer stadium — seemed to proceed with normal life as Oleg drove past glass-walled office buildings. “It looks like there is no war. Everything is quiet — peaceful,” he said. “And we will see how that will change now.”

He pulled up to the last rebel checkpoint before the road to the airport became a no-man’s-land. Shirtless men in dusty jeans worked feverishly in the fading sunlight, digging and stacking sandbags, with an eye to the approaching night. Then the sedan passed into the silence of the edge of war; the Ukrainian army was hidden in the distance somewhere. Oleg stopped the car in front of a flatbed truck. Bullet holes pocked the windshield; shoes and clothing scraps were scattered around. The back was caked in blood. Some 30 rebels had died there, Oleg said, when the truck was ambushed en route to the airport by a Ukrainian RPG team. The only sound on the deserted highway came from a billboard flapping in the wind overhead. “This cannot go without punishment,” Oleg said.

A silver van pulled up suddenly, and a man in a black cap pointed a submachine gun from the driver’s side window. “Who are you?” he shouted. A young couple, holding hands, approached on the sidewalk about 100 yards away, taking slow and deliberate steps toward an apartment building set back in the trees. Bursts of gunfire echoed nearby. Then the sedan was back onto Donetsk’s busy streets. “And now there is no war. So it’s a feature of civil war,” Oleg said, meaning that sometimes people don’t recognize it until it’s right upon them. “Most people still don’t understand that this is war. But when there will be more victims and more death, they will stand up.”

“You have to respond somehow to the killing,” said another man late that night. He called himself a scientist, and his name was Mikhail. To make a tally of the dead around the truck just after the attack, he had counted their heads, since the bodies were in pieces. Then he crept in his sandals through the woods, armed only with a folding knife. When he came upon a Ukrainian soldier, he said, he killed him with the 6-inch blade. Mikhail, 56, had served in Afghanistan, but it was different this time, killing his fellow Ukrainian. “Before it was an order,” he said. “Now it’s voluntary.”

He was sitting with friends inside a rebel-held building in the heart of the city, in a room where a small arsenal of guns leant against the walls. Half were old carabiners, half modern AK-74s — rebels were accumulating more weapons as they crawled deeper into the conflict. Mikhail put his folding knife on the table, and then produced the rifle of the soldier he said he had killed, with red stains along the shoulder strap. “It was covered in blood,” Mikhail said. “I washed it, and now it belongs to me.”

The Kiev government was stepping up what it had termed its “anti-terrorist operation,” and the men felt it pressing closer. They thought of it as retribution — “a punishment operation” — rained down from tanks and airplanes. The rebels in the room, all former Berkut, had created a battalion, hoping to act as police, but instead they were being drawn into the war. Their burly commander, a 57-year-old martial arts instructor named Yuriy Sivokonenko, worried for his family, and had tried to ensure that his two sons wouldn’t take up arms. His wife of 32 years, meanwhile, was breaking down, spending her days, he said, “crying and praying.”

Sivokonenko said he hoped for compromise as he served homemade cognac and jam that supporters had donated. But the possibility seemed to be shrinking; the conflict had reopened past wounds and the present had become polarized. He took a book from the armoire where he kept the cognac, describing it as a key to the truths he was fighting to defend — he had always held them, but now they felt threatened by those of his neighbors. It was a beautiful hardcover with grand illustrations, detailing a glorious history of the ethnic Russian people dating back to the 14th century. Shown the book the next morning, a local historian who supports the government would dismiss it as “fairy tales and myths.”

Mike Giglio is a correspondent for BuzzFeed News based in Istanbul. He has reported on the wars in Syria and Ukraine and unrest around the Middle East. His secure PGP fingerprint is 13F2 AD33 403F E72E 7C4E 5584 3E3B 2497 EEE9 DF7A